Fire Extinguisher Lab
Fuel, heat, and oxygen are all needed in the right
combination to produce fire. Combined, they are
called the “fire triangle”. By nature, a triangle needs
all three sides. Take away one of the sides, and the triangle collapses. The same is
true of fire. Take away any of the components of fire: fuel, heat, or oxygen, and the
fire collapses, meaning that it cannot burn.
Heat
A heat source is responsible for the initial ignition of fire, and heat is also
needed to maintain the fire and permit it to spread. Heat allows fire to spread by
removing the moisture from nearby fuel, warming surrounding air, and preheating
the fuel in its path, enabling it to travel with greater ease.
Fuel
Fuel is any kind of combustible material, and is characterized by its moisture
content (how wet the fuel is), size and shape, quantity, and the arrangement in
which it is spread over the landscape. The moisture content determines how easily
that fuel will burn.
Oxygen
Air contains about 21% oxygen, and most fires require at least 16% oxygen
content to burn. Oxygen supports the chemical processes that occur during a wild
fire. When fuel burns, it reacts with oxygen from the surrounding air releasing heat
and generating combustion products (i.e. gases, smoke, embers). This process is
known as oxidation.
Firefighters try to do just that- remove one of the three essential components of fire.
For example, when they dig a line around a fire, fuel is removed. When water is
dropped on a fire, it reduces the heat. Retardant, a thick, soupy substance, coats
fuels, blocking them from oxygen. If you think of fighting fire in terms of breaking
the fire triangle, then it’s easier to understand the tactics of firefighter.
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In your science journal copy your first journal assignment:
Journal #2: Different types of fires require you to remove different parts of
the fire triangle to extinguish them. Explain how you might remove a
different part of the fire triangle to put out an electrical appliance that
catches on fire compared to how you would put out a wood campfire.